if u want to using buttons use this it will work in unity 3d and ios

void OnGUI()
{
    if(GUI.RepeatButton(new Rect(Screen.width/10,Screen.height/1.5f,Screen.width/15,Screen.height/10),"up"))
    {
       transform.Translate(Vector3.forward*Time.deltaTime*50); 

    }

    if(GUI.RepeatButton(new Rect(Screen.width/10,Screen.height/1.15f,Screen.width/15,Screen.height/10),"down"))
    {
       transform.Translate(Vector3.back*Time.deltaTime*50);

    }

    if(GUI.RepeatButton(new Rect(Screen.width/40,Screen.height/1.3f,Screen.width/15,Screen.height/10),"left"))
    {
       transform.Rotate(Vector3.down, 90*Time.deltaTime);
    }

    if(GUI.RepeatButton(new Rect(Screen.width/5.6f,Screen.height/1.3f,Screen.width/15f,Screen.height/10),"right"))
    {
       transform.Rotate(Vector3.up, 90*Time.deltaTime);
    }
}

other wise, u can use joystick for the movement in ios. the standard package is present in standard assets mobile in the unity itself.
so u try it once.
In menu->assets->import package->standard assets(mobile)

I will be code in I appreciate in your kindness dude Thx a lot.